Controlling Niagara force with velocity of motion controller

Controlling Niagara force with motion controller
Hi all! I wondered if anyone has a tip on how to control a linear force or gravity force with the velocity of a VR motion controller? My problem right now is that I am only getting positivw values from thw velocity of the controller so I can only get the particles to move upwards. But I want to be able to move the force downwards when I move the motion controller downwards as well. Any solutions?